The overall objective is to investigate the physiology, including behavior, of the adult female mosquito, especially the endocrine control of digestion, egg maturation, sexual behavior, host attraction, and biting. The effect of aging on certain physiological events will be investigated, as we have found that some reproductive processes are slower as the female ages. This has important epidemioloical implications, because multiple blood-feeding during each gonotrophic cycle may become obligatory as the female ages. The ovary must be regarded as an endocrine organ, since it produces a hormone that stimulates vitellogenin synthesis by the fat body of blood-fed females and when the ovary retains a large enough number of eggs, it secretes a yolk inhibitor that suppresses development of less advanced oocytes. The relationship of these ovarian hormones to those secreted by the neurosecretory system and corpora alata (CA) will be investigated by ovarian transplantation and surgical ablation of the endorine tissues. We will try to develop a bioassay for CA hormone in circulation and to determine the duration of the dependence of deveoping oocytes on both the CA hormone and the neurosecretory hormone.